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T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
ring t a n k , 0, where it is agitated continuously b y means of compressed air, which also operates t h e automatic valve, through which t h e lime is delivcred t o t h e still. T h e timing of this valve is regulated b y a needle valve a n d by-pass between t h e t o p a n d bottom of a cylinder fillcd with kerosene, in which a piston descends a n d ascends. This makes i t possible t o supply t h e lime in small quantities and at frequent a n d regular intervals, making for uniform temperatures a n d regular operation. Steam is supplied t o t h e still through a n automatic valve also operated b y compressed air, t h e controller consisting of a thermostat, depending for its operation on t h e expansion o r contraction of a liquid, t h e pressure l h u s generated serving t o operate a small air valve which in t u r n controls t h e compressed air supply t o a diaphragm valve through a,hich steam is served t o t h e still. T h e thermostat is adjusted to operate at t h e temperature of t h e t o p of t h e still, a n d serves t o keep this temperature within a range of 2' F. of t h e predetermined point. T h e concentrate runs about 28 per cent NHI at all times a n d is diluted t o t h e desired degree as used. T h e cost of operation per io-hour d a y runs approximately as follows:
___ Output, 3,000Ibs. 26 per cent NHliOH Cost per 1,WO lbr. 26 per cent NH'OH..
$6.71
. . . ,. .. . . . . . 9 2 . 2 1
T h e outfit has proved t o be simple in construction and easy t o operate a n d t h e results more t h a n come u p to expectations. WBLSBACIICo.,GLOIICBSTIR. N.
1.
A NEW GLASS; AND AN APPLICATION OF THE LOW REFLECTIVITY OF GLASS FOR RADIANT HEAT BY 12. C. SOLLIYAN ASD W C. TAYLOR Received August 19, 1915
A glass has recently been developed which is unique among borosilicate glasses in t h a t i t combines very
Pig. I-a. Dish Silvered in Quarters Outside Cake Has Adhercd o v e r the Silvci b. W h e r e Protected by Silver, Cake is Light Colored and hiperfectly Baked: Brown and weii-none~ i ~ ~ ~ h
AS
R G .
B ~ E I Dr~ GLASS A N D Trw PIXY ~ ~ . REMOVED YXDM CVZS
low thermal expansion with great resistance to a t t a c k of reagents. It is of simple chemical composition, being frec from heavy metals a n d metals of t h e magnesium-calcium-zinc group. I t s charactcristic properties are due, in part, t o very high silica content which incidentally has necessitated special technique for
12
its melting a n d working. Some of the measured properties of the glass are as follows: Specific gravity 2.25. Mean linear expansion coefficient (1-350~) 0.0000032. ATTACK BY RBACBNTS: Water a t the boiling point dissolves several times as much from the best imported laboratory glass as from this glass. SOFTENING POINT: A thread I tnm. in diameter and 23 cm. in length suspended verticdly and heated through the upper 9 cm. elongates of its own weight a t the rate of I mm. per minute at 800' C. Culinary ware made of t h e glass was found t o bake food more rapidly t h a n earthenware or metal. T h e reason for this lay in the case of t h e mctal in t h e greater reflectisity of t h e metal for radiant energy. Magnus found t h a t silver reflected 83 t o go per cent, glass only 6 t o 14 per cent of the rays incident a t a n angle of 4 5 O . l while Hageu and Rubens* give gS t o 49 per cent as t h e proportion of heat reflected b y silvcr and Coblentz's3 curves indicate 3 t o I I per cent as thc reRection b y glass. T h e following experiment, devised b y Dr. J. T. Littleton, showed t h a t this difference in reflectivity is of practical importancc in t.he baking process: A tmkinp dislz was silvered oil the outer surface in alternate quarters and a cake baked in it in an ordinary kitchen oven over a gas flame. Where the cake had been protected by the metal coating the bottom aftm baking was light colored, sticky, and imperfcctly baked while in tlie other quarters it was brown and well done. Fig. I shows the interior of the dish with the cake adhering to i t over the silvered sections, also the cake 8s it was turned out bottom up with the quartering plainly visible. Experiments showing t h a t bread bakes Laster in glass than in kin were made b y baking equal quantities of dough in two glass bread pans and two tinned iron pans of t h e same internal dimensions. The metal pans had been in service for some time a n d their onter surfaces were somewhat tarnished. T h e pans were placed in the oven of a gas stove, the t v o glass pans diagonally opposite each other and t h c metal pans diagonally opposite each other. All four were left in t h e oven t h e same length of time. Tl'hen taken
Pic. I1 ~
Vol. 7 , No.
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